Did you ever play Red Dead Revolver? That one was on the PS2 and it was spectacular. I remember way back in like 2001 and Rockstar had promised a "GTA-Clone set in a Western Atmosphere". When they finally released RDR in 2004 I have to admit it wasn't a GTA-Sandbox Clone but it was definitely a very good game.
The Multi-Player was spectacular, really really fun. However I only played it on the Split Screen. I can only imagine that the Online Multi-Player is going to be extremely kick ass for this PS3 version.